Sun facts for kids
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| Observation data | |
|---|---|
| Average distance from Earth |
1.496×108 km 8 min 19 s at light speed |
| Visual brightness | −26.74 |
| True brightness | 4.83 |
| Angular size | 31.6–32.7′ |
| Adjective | Solar |
| Orbit and rotation | |
| Average distance from Milky Way center |
≈ 2.7×1017 km 27,200 light-years |
| Velocity | ≈ 220 km/s (orbit around the center of the Milky Way) ≈ 20 km/s (relative to average velocity of other stars nearby) ≈ 370 km/s (relative to the cosmic microwave background) |
| Obliquity | 7.25° (to the ecliptic) 67.23° (to the galactic plane) |
| Rotation velocity | 7.189×103 km/h |
| Physical characteristics | |
| Equatorial radius | 696,342±65 km 109 × Earth |
| Equatorial circumference | 4.379×106 km 109 × Earth |
| Flattening | 9×10−6 |
| Surface area | 6.09×1012 km2 12,000 × Earth |
| Volume | 1.41×1018 km3 1,300,000 × Earth |
| Mass | (1.98855±0.00025)×1030 kg 333,000 × Earth |
| Average density | 1.408 g/cm3 0.255 × Earth |
| Surface gravity | 274.0 m/s2 27.94 g 27,542.29 cgs 28 × Earth |
| Escape velocity (from the surface) |
617.7 km/s 55 × Earth |
| Temperature | Center: 1.57×107 K Photosphere: 5,778 K Corona: ≈ 5×106 K |
| Luminosity (Lsol) | 3.846×1026 W |
| Age | ≈4.6 billion years |
The Sun is the star at the very center of our Solar System. It's a yellow dwarf star that gives off lots of energy. This energy comes as light, heat, ultraviolet light, and radio waves. It also sends out a stream of tiny particles called "solar wind" that reaches Earth.
All this energy comes from nuclear fusion happening deep inside the Sun. Nuclear fusion is a powerful reaction where hydrogen atoms combine to form helium, releasing huge amounts of energy.
The Sun is a star, just like many others in our Milky Way galaxy. It's known as a G-type main-sequence star based on its type. The Sun has been around for about 4.5 billion years and is expected to shine for at least that much longer. It is about 100 times wider than Earth. Its mass is 1.9891×1030 kg, which is 333,000 times the mass of Earth. About 1.3 million Earths could fit inside the Sun!
Every second, the Sun changes about 600 million tons of hydrogen into helium. The energy made in the Sun's core can take a very long time to escape, sometimes between 10,000 and 170,000 years.
Contents
How the Sun Formed
Scientists believe the Sun began from a giant cloud of dust and small ice pieces about 4.567 billion years ago.
In the middle of this huge cloud, gravity pulled all the material together into a ball. When this ball became big enough, the immense pressure inside started a fusion reaction. The energy released from this reaction made the ball heat up and start to shine brightly.
The radiation (energy) from the new Sun pushed the rest of the cloud away. The planets in our Solar System then formed from the remaining parts of this cloud.
What the Sun is Made Of
The Sun is mostly made of hydrogen and helium. All other elements, which are heavier than hydrogen and helium, make up less than 2% of the Sun's total mass.
The Sun's chemical makeup comes from the interstellar medium (the gas and dust between stars). Most of the hydrogen and helium in the Sun were created during the Big Bang nucleosynthesis in the first 20 minutes of the universe. The heavier elements were made by stars that died before the Sun was born. These heavier elements were released into space when those stars exploded as supernovae.
The Sun's Surface: The Photosphere
This layer is what we see as the "surface" of the Sun. The light that reaches Earth from the Sun comes from this layer. Below the photosphere, the Sun is opaque, meaning light cannot pass through it.
The Sun's Atmosphere
The Sun has five layers in its atmosphere. The chromosphere, transition region, and corona are much hotter than the outer photosphere. Scientists think that Alfvén waves might help heat the corona.
The minimum temperature zone is the coolest layer of the Sun. It's about 500 kilometers (310 miles) above the photosphere. Its temperature is around 4,100 K. This part of the Sun is cool enough for simple molecules like carbon monoxide and water to form. We can see these molecules using special tools called spectroscopes.
The chromosphere is the first layer of the Sun that we can actually see. It's best seen during a solar eclipse when the Moon blocks most of the Sun's bright light.
The solar transition region is a part of the Sun's atmosphere between the chromosphere and the outer corona. We can observe it from outer space using telescopes that detect ultraviolet light. This region is a boundary between two very different layers. At the bottom, it touches the photosphere, and gravity shapes its features. At the top, it connects to the corona.
The corona is the Sun's outer atmosphere and is much larger than the rest of the Sun. The corona constantly expands into space, forming the solar wind which fills our entire Solar System. The average temperature of the corona and solar wind is about 1 to 2 million K. In the hottest areas, it can reach 8 to 20 million K. Scientists are still trying to understand why the corona is so hot. We can see it during a solar eclipse or with a special instrument called a coronagraph.
The heliosphere is the very thin outer atmosphere of the Sun. It is filled with the solar wind plasma. It stretches out beyond the orbit of Pluto to the heliopause. At the heliopause, it meets and interacts with the interstellar medium.
What We Can See on the Sun
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Since the Sun is made of gas, its "surface" features are always changing. If you look at the Sun through a special solar telescope, you might see dark areas called sunspots. These spots are caused by the Sun's strong magnetic field. Sunspots only look dark because the rest of the Sun is incredibly bright.
Some space telescopes, including those that orbit the Sun, have seen huge arches of the Sun's material suddenly shoot out. These are called solar prominences. Solar prominences come in many shapes and sizes. Some are so big that Earth could fit inside them! Solar flares are also powerful bursts of energy that come and go.
Sunspots, prominences, and flares become rare, then numerous, and then rare again, following a cycle of about 11 years.
Eclipses
A solar eclipse happens when the Moon passes directly between the Earth and the Sun, blocking the Sun's light. The last total solar eclipse on December 26, 2019, was seen in Saudi Arabia, India, Sumatra, and Borneo. Parts of Australia and Asia saw a partial eclipse.
A lunar eclipse occurs when the Moon passes through Earth's shadow. This can only happen during a full moon. There can be anywhere from 0 to 3 lunar eclipses in a single year. Partial lunar eclipses happen a bit more often than total ones.
Solar Weather and Its Effects
Solar weather, also called space weather, affects us on Earth. It includes sunlight and the solar wind. Solar flares can shoot out a lot of very hot gas from the Sun. If a solar flare is aimed towards Earth, fast-moving protons (tiny particles with a positive electric charge) can hit our planet. This can cause a solar storm.
Solar storms can lead to electrical blackouts or block radio signals. They can also damage satellites orbiting Earth. The radiation from an extreme solar storm could be very dangerous for astronauts, so they need protection. Luckily, Earth’s magnetic field and atmosphere usually protect us from these flares.
Solar flares can also create an aurora. Auroras look like beautiful, shimmering curtains of light in the sky. They are called Northern Lights (Aurora Borealis) if seen near the North Pole. They are called Southern Lights (Aurora Australis) if seen near the South Pole. Solar weather also affects other planets. We have pictures of auroras on every planet except Mercury and Pluto.
Just like we get Earth weather forecasts, we can get Solar weather forecasts. Scientists study the Sun to predict when flares will happen. They try to tell when solar storms will reach Earth or other parts of the Solar System.
The Sun's Planetary System
The Sun has eight known planets orbiting it. These include four rocky planets (Mercury, Venus, Earth, and Mars), two gas giants (Jupiter and Saturn), and two ice giants (Uranus and Neptune). Our Solar System also has at least five dwarf planets, an asteroid belt, many comets, and a large number of icy objects beyond Neptune's orbit.
Observing the Sun and Its Effects
Looking directly at the bright Sun with your naked eye can cause pain. However, doing so for very short times is usually not harmful to normal eyes.
But, looking at the Sun through binoculars or a telescope can cause permanent eye damage. These tools focus sunlight, making it much more intense.
Partial solar eclipses are dangerous to view directly. This is because your eye's pupil doesn't adjust well to the unusual contrast between the bright sliver of Sun and the dark sky.
Ultraviolet light from the Sun can kill germs and can be used to clean tools and water. It also causes sunburn and has other effects like helping your body make vitamin D and causing sun tanning.
Earth's ozone layer greatly reduces the amount of UV light that reaches us. So, the amount of UV light varies a lot depending on your latitude. This has led to many biological adaptations, including different human skin colors in various regions of Earth.
Exploring the Sun
Early space probes designed to study the Sun included NASA's Pioneers 5 through 9 and the Helios 1 and 2. These missions in the 1950s, 60s, and 70s collected a lot of information about the Sun. The Parker Solar Probe is a NASA robotic spacecraft launched in 2018. It is currently traveling to study the Sun's outer corona.
The Parker Solar Probe will get as close as 9.86 solar radii (6.9 million kilometers or 4.3 million miles) from the Sun's center. By 2025, at its closest point, it will travel as fast as 430,000 kilometers per hour (267,000 miles per hour), or 0.064% the speed of light.
The project cost US$1.5 billion. Johns Hopkins University Applied Physics Laboratory designed and built the spacecraft. It was launched on August 12, 2018. It was the first NASA spacecraft named after a living person, honoring physicist Eugene Parker, a professor at the University of Chicago.
A memory card with the names of over 1.1 million people was placed on a plaque on the spacecraft on May 18, 2018. The card also has photos of Parker and a copy of his 1958 scientific paper about solar physics.
On October 29, 2018, the spacecraft became the closest human-made object to the Sun ever. The previous record was set by the Helios 2 spacecraft in April 1976, at 26.55 million miles from the Sun's surface.
The Sun's Future
Astrophysicists say our Sun is a G-type main-sequence star that is in the middle of its life. In about a billion years, the Sun's increased energy will boil away Earth's atmosphere and oceans.
In a few more billion years, scientists think the Sun will grow much bigger and become a red giant star. The Sun could become up to 250 times its current size, possibly even swallowing Earth.
Earth's exact fate is still a bit of a mystery. For the next 5 billion years, the Sun will be fairly stable. Calculations suggest that Earth might move to a wider orbit. This is because about 30% of the Sun's mass will be blown away by the solar wind. However, in the very long term, Earth will likely be destroyed as the Sun expands. Stars like the Sun become red giants later in their lives. The Sun will expand beyond the orbits of Mercury, Venus, and probably Earth. Even before that, Earth's oceans and air would have disappeared.
After the Sun reaches its largest size, it will lose its outer layers and form a planetary nebula. Eventually, the Sun will shrink into a white dwarf. Then, over hundreds of billions or even a trillion years, the Sun would slowly fade into a black dwarf.
Images for kids
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Taken by Hinode's Solar Optical Telescope in January 2007
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Visible light photograph of sunspot, 13 December 2006
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The heliospheric current sheet extends to the outer reaches of the Solar System, and results from the influence of the Sun's rotating magnetic field
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Illustration of the Milky Way, showing the location of the Sun
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Map of the full Sun by STEREO and SDO spacecraft
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The Trundholm sun chariot pulled by a horse is a sculpture believed to be illustrating an important part of Nordic Bronze Age mythology 1350
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Sol, the Sun 1550
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The Sun giving out a large geomagnetic storm in March 2012
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A solar prominence erupts in August 2012
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The Sun, as seen from low Earth orbit overlooking the International Space Station.
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Halo with sun dogs
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A sunrise
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The Sun as it is seen from Earth
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In this false-color ultraviolet image, the Sun shows a C3-class solar flare (white area on upper left), a solar tsunami (wave-like structure, upper right) and multiple filaments of plasma following a magnetic field, rising from the stellar surface
See also
In Spanish: Sol para niños
